Abstract:We present a comprehensive evaluation of uncertainties in the Global Warming Potential (GWP) and Global Temperature Change Potential (GTP) of CH4, using a simple climate model calibrated to AOGCMs and coupled climate-carbon cycle models assessed in the IPCC Fourth Assessment Report (AR4). In addition, we estimate uncertainties in these metrics probabilistically by using a method that does not rely on AOGCMs but instead builds on historical constraints and uncertainty estimates of current radiative forcings. While our mean and median GWPs and GTPs estimates are consistent with previous studies, our analysis suggests that uncertainty ranges for GWPs are almost twice as large as estimated in the AR4. Relative uncertainties for GTPs are larger than for GWPs, nearly twice as high for a time horizon of 100 years. Given this uncertainty, our results imply the possibility for substantial future adjustments in best-estimate values of GWPs and in particular GTPs.

Also just in from the settled science:Decadal changes in tropical convection suggest effects on stratospheric water vapor in GRL by George Tselioudis, Eric Tromeur, William B. Rossow and C. S. Zerefos

Analysis of satellite observations of tropical Weather States derived from a cluster analysis of ISCCP cloud property retrievals, shows that the deep convection Weather State increased in frequency from 1983 to about 2000 and remained at a nearly constant level after that. The sharpest deep convection increase occurred between 1993 and 2000. This convection variability is driven by changes that occur in the Indian Ocean and the Western-Central Pacific regions, which are the regions where the majority of deep tropical convection occurs. Analysis modifications to account for satellite coverage changes during the period under examination do not alter these findings. Previous studies showed that stratospheric water vapor increased from 1980 to 2000 and dropped after that to lower levels that persist until today, and that this change could explain part of the recent global temperature variability. Since tropical deep convection is an important mechanism affecting stratospheric water vapor concentrations, the observed decadal changes in tropical deep convection could explain in part the stratospheric water vapor variability patterns.

"The hard-hitting analysis by Rogelj, Meinshausen and colleagues highlights the increasing divergence between political rhetoric and the actions that would be needed to achieve the stated long-term goals. Rogelj and colleagues analysed two potential outcomes from the Copenhagen Accord, a pessimistic one where countries do only the minimum they pledged, and an optimistic one where all countries adhere to the most stringent end of their pledged emissions reductions without using any additional credits from forestry or banked credits from the Kyoto Protocol's first commitment period.

"Even in the optimistic case, the weak emissions targets for 2020 and the even weaker or absent targets for 2050 by many countries imply a greater than 50% chance that global warming will exceed 3°C by 2100. In the pessimistic case, which is more likely to become reality if the Copenhagen Accord is not turned into a strong and legally binding agreement, long-term warming is likely to be even greater.

"More than 130 countries, including the New Zealand government, agreed under the Copenhagen Accord to limit warming to 2°C. Hopes to actually achieve this goal are fading rapidly and irreversibly, because the concrete commitments by countries do not match the level of ambition that is needed. Given the weak 2020 emissions reduction targets, global emissions would need to be reduced subsequently from 2021 to 2050 by 3 to 3.5% per year, every year, to leave at least an even chance of not exceeding 2°C. None of the climate policies and measures currently contemplated, let alone implemented, has an even remote chance of achieving and sustaining such rapid emissions reduction rates post-2020.

"This analysis shows that it is imperative to substantially strengthen the emissions targets for 2020 as part of a strong international agreement if the world is to have a realistic chance of limiting warming to 2°C. We are no longer gambling the future of the planet - if we stick with current emissions targets we are folding our cards entirely and leaving it to our (and other people's) kids to pay our accumulated debts."

"The aim of limiting global warming to 2°C seems to become more difficult to achieve every day. The analysis by Joeri Rogelj and his colleagues shows that even the most optimistic interpretation of current plans by the leading countries is not on track. The key question is whether it is just not on track YET, or whether the current approach to dealing with climate change will ever get there.

"The UNFCCC meeting last December spent a lot of time talking about keeping global warming to 1.5°C. The credibility of doing that, when we do not yet seem to have any clear way of even keeping to 2°C, was challenged by scientists at a Royal Society meeting in London recently.

"These criticisms reflect a growing concern that the global policy process is becoming disconnected from reality. The basic issue is whether to rapidly accelerate technological development or continue to focus on using last century's technology to make more profits. So the key question is whether the current UNFCCC process influences that to any extent.

"It is becoming increasingly obvious that dealing with climate change is something that needs to become driven by society more broadly. People need to consider how much of a problem we want to pass on to our grandchildren and tell politics and industry to act accordingly. " -http://www.scoop.co.nz/stories/SC1004/S00057.htm

You might want to ask him directly, but I assume he struggles with the wave-particle duality of light just like other physicists. I recall him saying though, "Schrödinger didn't like particles and neither do I" or something to that effect.